Co-translational formation of disulfides guides folding of the SARS-CoV-2 receptor binding domain.
Co-translational formation of disulfides guides folding of the SARS-CoV-2 receptor binding domain.
复制标题
二硫键的共翻译形成引导 SARS-CoV-2 受体结合域的折叠。
DOI：
10.1016/j.bpj.2023.07.002
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发表时间：
2023
影响因子：
3.4
通讯作者：
Shakhnovich,EugeneI
中科院分区：
文献类型：
--
作者：
Bitran,Amir;Park,Kibum;Serebryany,Eugene;Shakhnovich,EugeneI
许多分泌蛋白质，包括病毒蛋白质，含有多个二硫键。二硫键的形成是如何与细胞中的蛋白质折叠相结合的，在分子水平上仍然知之甚少。在这里，我们结合联合收割机实验和模拟来解决这个问题，因为它涉及到SARS-CoV-2受体结合域（RBD）。我们表明，RBD只能可逆地重折叠，如果其原生二硫化物折叠前存在。但在它们不存在的情况下，RBD自发地错误折叠成非天然的熔融球样状态，其在结构上与完全二硫键形成不相容，并且非常容易聚集。因此，RBD天然结构代表了蛋白质能量景观上的亚稳态，二硫化物减少，表明需要非平衡机制来确保折叠前形成天然二硫化物。我们的原子模拟表明，这可能是通过在RBD分泌到内质网的共翻译折叠。也就是说，在中间翻译长度下，预测天然二硫键对以高概率聚集在一起，因此，在合适的动力学条件下，该过程可以将蛋白质锁定在其天然状态，并避开高度聚集倾向的非天然中间体。RBD折叠景观的详细分子图像可能揭示SARS-CoV-2病理学和控制SARS-CoV-2进化的分子限制。
Many secreted proteins, including viral proteins, contain multiple disulfide bonds. How disulfide formation is coupled to protein folding in the cell remains poorly understood at the molecular level. Here, we combine experiment and simulation to address this question as it pertains to the SARS-CoV-2 receptor binding domain (RBD). We show that the RBD can only refold reversibly if its native disulfides are present before folding. But in their absence, the RBD spontaneously misfolds into a nonnative, molten-globule-like state that is structurally incompatible with complete disulfide formation and that is highly prone to aggregation. Thus, the RBD native structure represents a metastable state on the protein's energy landscape with reduced disulfides, indicating that nonequilibrium mechanisms are needed to ensure native disulfides form before folding. Our atomistic simulations suggest that this may be achieved via co-translational folding during RBD secretion into the endoplasmic reticulum. Namely, at intermediate translation lengths, native disulfide pairs are predicted to come together with high probability, and thus, under suitable kinetic conditions, this process may lock the protein into its native state and circumvent highly aggregation-prone nonnative intermediates. This detailed molecular picture of the RBD folding landscape may shed light on SARS-CoV-2 pathology and molecular constraints governing SARS-CoV-2 evolution.